q11_1: Does the job in question 11 of Comercio.xlsx
In mathphysmx/cleanTable: Cleaning of data in tables.

1	q11_1(x, sc, ec, fw = 0, col_fw = 1, cols = NULL)

`x`	data.frame or matrix with data. The last column is assumed to be the total column.
`sc`	Character. start column name.
`ec`	Character. End column name. This is the column of totals.
`col_fw`	corresponding column to add values with in case the computed sum is less than given by `x`. Default to `1`.
`cols`	columns to be used to check the sum. It overrides `sc` and `ec`

q11_1(x = df1, sc = "P11_1_1", ec = "P11_1_6")
cpos <- getPosIndex(cnames = names(df1),
                    sc = "P11_1_1", ec = "P11_1_6")
q11_1(x = df1, cols = cpos)